Patent Documents 1 to 3 disclose electrostatic speakers. The electrostatic speakers include a vibration portion. The vibration portion includes a dielectric layer and a pair of electrode layers. The pair of electrode layers are placed on the front and back surfaces of the dielectric layer.
If a bias voltage having a signal wave based on sound being superimposed thereon is applied to the pair of electrode layers, the voltage between the pair of electrode layers varies according to a change in the sound. Electrostatic attraction between the pair of electrode layers changes accordingly. As the electrostatic attraction changes, the dielectric layer is deformed, and the vibration portion vibrates. The electrostatic speaker reproduces the sound by using this vibration.